Large-scale mouse gene targeting projects, such as KOMP, EUCOMM and NorCOMM, promise to deliver a vast number of conditional loxP-flanked alleles to the scientific community. Capitalizing on this resource will require that a large, diverse set of well-characterized Cre driver lines be made available to researchers around the world. The Jackson Laboratory (JAX) houses and distributes the single largest collection of Cre driver strains, including 69 that are currently distributed as live colonies. Despite the best efforts of those developing new Cre lines, the fidelity of Cre activity is not always ideal. Many difficulties have been reported in various Cre lines, including mosaic or incomplete deletion in a target tissue/cell type, inconsistent activity, expression in non-target tissues, and/or Cre-related toxicity. In many cases, however, these data are not reported or available to the potential user. The overall objective of this proposal is to improve the utility of the Cre driver lines by developing a high-throughput pipeline to systematically address these issues, characterize a subset of Cre lines currently housed in the JAX Repository and to provide the information to the scientific community. To accomplish this task, we will develop assays and protocols to extend the characterization of Cre driver line functionality. This will include evaluation of excision in both target and non-target tissues, and also will address toxicity, sex-specific functional transmission, and consistency of excision. Using these protocols, we will then comprehensively characterize a set of Cre driver lines currently available as live colonies in the Jax Repository, which will serve as a model for characterization of all Cre lines in the future. These data are intended to fill in where published information leaves off, providing essential quality control data and facilitating the identification of appropriate lines for potential users. This effort will be integrated with ongoing efforts of Mouse Genome Informatics to house and display Cre line data and by the development of a JAXCre website to disseminate data on Cre driver lines. As the Repository holding the greatest number of Cre driver lines by far, The Jackson Laboratory is in a perfect position to acquire and disseminate this essential information. By developing a high-throughput flow scheme for extended characterization of Cre lines, we will be able to attack this problem, and enhance the value of these lines for the scientific community. PUBLIC HEALTH RELEVANCE: The mouse is an invaluable tool for modeling human disease. The tremendous power of the mouse is due in part to our ability to manipulate its genome in a precise manner, and our toolbox to perform these tasks is rapidly expanding. As part of The Jackson Laboratory Repository, this proposal seeks to leverage our mouse and informatic resources to enhance the value of mouse tool strains for the scientific community. Because of our position as a central resource utilized by thousands of scientists around the world, this project promises to have an important impact on the development of new models of human disease.